Over the past approximately 20 years, high efficiency fill material in the form of thin sheets of PVC has been used as cooling tower fill media. See J. S. Gill et al., "Fouling of Film Forming Cooling Tower Fills--A Mechanistic Approach", Cooling Tower Institute Annual Meeting (Houston, Tex., 1994). Because of its greater heat transfer efficiency and lower weight it has been received favorably by the industry. A problem with this fill material is that it has a tendency to foul rapidly with water borne materials and develops significant deposits commonly containing microorganisms and silt. Studies have shown that the microorganisms provide a matrix or "glue" for further deposition of silt, primarily clay, especially when the makeup is from a fresh water surface supply. Id. It is common for biofilms in industrial water systems to collect or capture abiotic particles including clay particles. See E. J. Bower, "Theoretical Investigation of Particle Deposition in Biofilm Systems", Water Research, 21:1489-1498 (1987); W. J. Drury et al., "Interactions of 1 .mu.m Latex Particles in Pseudomonas aeruginosa Biofilms", Water Research, 27:1119-1126 (1993); W. J. Drury et al., "Transport of 1 .mu.m Latex Particles in Pseudomonas aeruginosa Biofilms", Biotechnol. Bioeng., 42:111-117 (1993); W. G. Characklis, "Microbial Fouling", in W. G. Characklis and K. C. Marshall (eds.), Biofilms, pp. 523-584 (John Wiley, New York, 1990). In the case of clay crystals, Marshall, in Interfaces in Microbial Ecology, (Harvard Univ. Press, Cambridge, Mass., 1976), presented electron microscopic evidence of clay-bacterial associations. He presented results indicating that the clay crystals associated in an edge-to-edge manner to carboxyl-type bacterial surfaces, with the positively-charged edges of the clay crystal attracted to the negatively charged bacterial surface. These observations were supported by J. S. Gill et al., supra, in which a complex scanning electron microscopic procedure was used to view bacterial-clay interactions on the PVC fill surface.
Different treatments have been proposed to control fouling of PVC fill material in recirculating cooling water. Pearson, et al., "Cleaning and Maintenance of Film Fill at Florida Power Corporation", Cooling Tower Institute Annual Meeting, 1992, Technical Paper No. TP92-09, utilized a 60% acrylic acid, 40% 2-acrylamido-2-methylpropylsulfonic acid (AA/AMPS copolymer) to control the fouling onto pvc fill material in a seawater fed system. Mortensen and Conley, "Film Fill Fouling in Counterflow Cooling Towers: Research Results", National Association of Corrosion Engineers Annual Meeting, 1994, Paper No. 457, recommended microbiological control with the use of microbiocides and with possible pretreatment of the makeup water using some type of clarification.
Others have documented that nonionic surfactants may affect the adhesion of bacteria to surfaces. L. R. Robertson, "Prevention of Microbial Adhesion", Biological Sciences Symposium, TAPPI Proceedings, Minneapolis, MN, Oct. 3-6, 1994, pp. 225-232; C. L. Wiatr, "Development of Biofilms", Biological Sciences Symposium, TAPPI Proceedings, Minneapolis, Minn., Oct. 3-6, 1994, pp. 225-232; B. L. Blainey and K. C. Marshall, "The Use of Block Copolymers to Inhibit Bacterial Adhesion and Biofilm Formation on Hydrophobic Surfaces in Marine Habitates", Biofouling, 4: 309-318 (1991); J. H. Paul and Jeffrey, "Evidence for Separate Adhesion Mechanisms for Hydrophilic and Hydrophobic Surfaces in Vibrio proteolytica", Appl. Environ. Microbiol., 50: 431-437 (1985); W. K. Whitekettle, "Effects of Surface-Active Chemicals on Microbial Adhesion", Jour. Indust. Micrbiol., 7: 105-116 (1991); H. F. Ridgeway et al., "Bacterial Adhesion and Fouling of Reverse Osmosis Membranes", Journal AWWA, July, 1985, pp. 97-106; J. Olsson et al., "Surface Modification of Hydroxyapatite to Avoid Bacterial Adhesion", Colloid Polym. Sci., 269 (12): 1295-1302 (1991).